Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and a rotor having a rotatable hub with one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
The rotor blades generally include a suction side shell and a pressure side shell typically formed using molding processes that are bonded together at bond lines along the leading and trailing edges of the blade. Further, the pressure and suction shells are relatively lightweight and have structural properties (e.g., stiffness, buckling resistance and strength) which are not configured to withstand the bending moments and other loads exerted on the rotor blade during operation. Thus, to increase the stiffness, buckling resistance and strength of the rotor blade, the body shell is typically reinforced using one or more structural components (e.g. opposing spar caps with a shear web configured therebetween) that engage the inner pressure and suction side surfaces of the shell halves. The spar caps are typically constructed of various materials, including but not limited to glass fiber laminate composites and/or carbon fiber laminate composites. The shell of the rotor blade is generally built around the spar caps of the blade by stacking layers of fiber fabrics in a shell mold. The layers are then typically infused together, e.g. with a thermoset resin.
In addition, methods for manufacturing wind turbine rotor blades may include forming the rotor blades in blade segments. The blade segments may then be assembled to form the rotor blade. For example, some modern rotor blades, such as those blades described in U.S. patent application Ser. No. 14/753,137 filed Jun. 29, 2105 and entitled “Modular Wind Turbine Rotor Blades and Methods of Assembling Same,” which is incorporated herein by reference in its entirety, have a modular panel configuration. Thus, the various blade components of the modular blade can be constructed of varying materials based on the function and/or location of the blade component. More specifically, the blade segments may be constructed of a thermoplastic material and/or a thermoset material.
Methods of joining thermoset components to each other as well as to thermoplastic materials continue to be an issue. For example, joining predominately thermoset parts and/or joining a predominately thermoset part with a thermoplastic part conventionally requires the use of expensive adhesives and/or fasteners, both of which add weight and cost to the blade. As such, it is advantageous to use thermoplastic rotor blade components where possible so that like components can be easily joined, e.g. via thermoplastic welding.
Even still, thermoplastic welding of blade components also has issues that need to be addressed. For example, one challenge with current thermoplastic welding techniques involves maintaining intimate contact between the surfaces to be welded throughout the heating and cooling cycle of the welding process.
Thus, the present disclosure art is directed to improved thermoplastic welding techniques for rotor blade components that address the aforementioned issues.